The invention relates to systems and methods for transporting associated data signals over a network, and more specifically to systems and methods that manage network resources by comparing characteristics of multiplexed and non-multiplexed data traffic.
Data networks are complex systems. Each data network can comprise thousands of nodes each of which can send and receive data. Accordingly, at any given time a data network can be simultaneously transporting many data signals between the various nodes of the network. To manage this data traffic, the network must constantly manage its resources. Specifically, network resources must be allocated by the network in a manner that ensures that the network can provide the necessary resources, such as available buffer memory, available link bandwidth, and other such resources, that are needed to support a connection, or route, between two or more nodes on the network.
Additionally, network resources must constantly be managed so that each of the many data signals being transported across the network have a sufficient service quality. For example, video data traffic must be managed by the network so that it is delivered from the source to the user in real time thereby allowing the user to view the video without sporadic interruptions that can arise when data delivery through the network is delayed for an unacceptable period of time. Therefore, as can be seen from above, a network must constantly manage the data traffic on the network. The act of managing the data traffic includes making sure that the flow of data traffic across the network occurs on path that has sufficient resources to support that data traffic flow. For example, the network must manage its resources such as its memory buffers, link bandwidth, address spaces, and other network resources to make sure that the data being routed from a source to a user can be delivered across the selected path and can be done so with an acceptable quality of service.
To address the issue of network management, network engineers generally address two problem domains. A first problem domain involves reducing the amount of data traffic that occurs across the network. A typical approach for reducing the scale of data traffic is to compress data signals from a large format into a smaller format thereby reducing the actual amount of data that needs to be transferred in order to send a data signal from one point to another. One technique involves compressing a data signal to generate a new data signal that has the same, or similar information content within that signal but can be represented with fewer data bits. Although data compression can work quite well for reducing the size of data signals that have to be transferred across the network, compressed digital signals are however often more inherently complex to transfer. This complexity arises from the fact that a compressed digital signal has an inherently variable bit rate. For example, a compressed digital video signal has a variable bit rate as the complexity and motion content of that digital video signal affects the compression process, allowing certain portions of the video signal to be more greatly compressed than other portions. The differences in compression result in different bit rates for certain portions of the video signal. Thus, a compressed video signal can have a substantially varying bit rate during the time of the data transfer. Although compressing a signal, such as a video data signal, can reduce the amount of the traffic that has to be transferred across the network, the compression technique creates a variable bit rate data signal thereby making it more difficult for the network to manage its resources to make sure that the proper resources are always available for supporting the variable bit rate signal, even when the variable bit rate signal is transferring at its peak rate, which can be substantially greater than the average bit rate for that signal.
To further shape traffic for efficient delivery, some networks employ multiplexing systems that can multiplex a plurality of variable bit rate signals to form a composite bit rate signal that has certain traffic characteristics, such as an average bit rate, and a predictable peak rate below a certain predetermined criteria. Such a composite signal can allow for the transfer of multiple variable bit-rate (VBR) signals in a manner that requires less network resources than would be required for transporting each of the data signals independently.
The second problem domain addressed by network engineers involves making network management systems that manage and allocate network resources more efficiently. This type of traffic control system is capable of analyzing the traffic on the data network, and making decisions based on the characteristics of this traffic as to how the data should be transferred so that the network can carry more data for the users while meeting quality of service (QoS) requirements.
Network resource management typically involves allocating resources so that the network provides the necessary buffering and link bandwidth that is needed to support a connection, or route, and its associated service quality, which is typically measured by bounded throughput, delay and loss. The network management system makes decisions on whether to admit the connections or whether to reserve resources, and other decisions each of which is based on a description of the traffic and an assessment of the available network resources at a given time. For example, the network resource management system can respond to a user""s request for the transport of a data signal by analyzing the traffic on the network to determine if the network has sufficient resources to support this new connection. Only if the network resource management system determines that such resources are available will it accept the user""s connection request.
To make its decision the network resource management system analyzes a description of the source traffic as well as a description of the required QoS. For networks that carry multiplexed groupings of associated VBR signals, the network management system must first demultiplex with the composite signal, or through some other means get information that is representative of the traffic characteristics of the individual signals in the composite signal to make the admission and resource allocation decisions. This often requires the cumbersome step of separating or demultiplexing the composite video signal into its individual sources to determine the known traffic characteristics for each of these individual sources. The network resource management system employs the traffic characteristics of the individual sources to determine whether the network can support carrying the new data signal requested by the user.
Although multiplexed VBR signals can add to a reduction in the amount of resources required by a network to transport traffic across the network, existing network resource management systems make routing decisions based on the traffic characteristics of individual signals. Accordingly, systems demultiplex the composite VBR signal to determine characteristics of the associated independent VBR signals. Therefore, network resource management is done based on the network characteristics of the independent signals and not the composite VBR signal. Accordingly, there is a need in the art for a network resource management system that can make resource management decisions based on the traffic characteristics of multiplexed VBR signals.
The invention provides methods for managing resources of a network so that data signals can be carried more efficiently. More particularly, a link in a network over which a data signal can be carried is identified, and it is determined whether the data signal can be carried over the link as a part of a multiplexed signal. Network resources for delivering the data signal as part of a multiplexed signal are compared with network resources for delivering the data signal as a separate signal. Admit decisions and network resource allocation decisions are made based on the result of this comparison.
More particularly, in one embodiment, the invention provides methods for carrying a data signal over a network. These methods may operate by identifying a link in the network over which the data signal can be carried, determining whether the data signal can be carried over the link as a part of a multiplexed signal, comparing network resource demands for delivering the data signal as part of a multiplexed signal with network resource demands for delivering the data signal directly, and allocating network resources for the data signal as a result of the comparison. The comparison of resource demands may involve comparing a plurality of different factors including buffer occupancy, and link bandwidth utilization. Similarly, these methods may compare network resources for maintaining or achieving desired efficiencies in resource utilization. Additionally, these methods may compare network resources for achieving or maintaining desired criteria of service quality, and to this end may include comparing network resources to a set of threshold criteria for achieving selected service quality and selected bandwidth utilization.
To implement a decision as to how a data signal is to be carried over the network, methods described herein provide a multiplexed signal by multiplexing the data signal being admitted to the network with another signal or signals already being carried by the network. In other embodiments, the process performs a link by link analysis of the network resources that would be allocated for delivering a requested signal. Thus, for a multi-link path, the methods described herein may analyze and compare network resource demands for each link in a path, as well as the resource demands for an entire path. Accordingly, it will be understood that the methods described herein can include selecting between multiple possible paths across a network based on a comparison of resources allocated for delivering the requested signal as an independent or as part of a multiplexed signal.
Methods described herein may be used to identify a data path and for the data path identified, to determine whether a data signal can be associated with a multiplexed signal being carried over a network. If so, other data signals in the multiplexed signal may be identified, and network resources for delivering the data signal as part of the multiplexed signal may be compared with delivering the data signal and the other data signals in the multiplexed signal independently of one another over the network.
In a further aspect, the invention can be realized as a data network for transferring a data signal. Such data network systems may include a first node and a second node, at least one link connecting the first and second nodes and capable of transferring the data signal there between, and a comparator capable of comparing network resource demands for delivering the data signal across the link as part of a multiplexed signal with network resource demands for delivering the data signal directly across the link. The comparator may be configured for comparing network resources to provide efficiencies in resource utilization, as well as being configured for comparing network resources representative of quality of service. The comparator may compare network resources for each link in each path identified by a path identifier, to select a path for delivering the data signal.